Troponin T has been used successfully to risk stratify patients with acute coronary syndromes, but the utility of this approach using a rapid bedside assay in patients undergoing thrombolysis for ST-segment elevation acute myocardial infarction has not been assessed in a large population. We assessed whether a point-of-care, qualitative troponin T test at enrollment could independently risk-stratify patients randomized to receive alteplase or reteplase in the GUSTO-III trial. Complete troponin T data were available for 12,666 patients (84%) enrolled at 550 hospitals. The primary end point was mortality at 30 days, and the predictive ability of an elevated baseline troponin T level was analyzed (after adjustment for baseline characteristics) with multiple logistic regression. Patients with an elevated troponin T result at enrollment (8.9%) had significantly higher mortality at 30 days (unadjusted 15.7% vs 6.2% for negative patients; p = 0.001), which persisted even after adjustment for age, heart rate, location of infarction, Killip class, and systolic blood pressure. In a multivariable regression model, a positive troponin T result added independently to the prediction of 30-day mortality (chi-square 46, p = 0.001). A positive result with qualitative troponin T testing on admission is an independent marker of higher 30-day mortality. Troponin T testing could be a valuable addition to the evaluation strategy for patients with acute myocardial infarction.